AN AB-INITIO PSEUDOPOTENTIAL CALCULATION OF GROUND-STATE AND EXCITED-STATE PROPERTIES OF GALLIUM NITRIDE

In this work, the electronic, ground-state and vibrational properties of both alpha-GaN (i.e. wurtzite structure) and the recently fabricated beta-GaN (i.e. zincblende structure) have been studied using the ab initio pseudopotential method within the local density approximation and a simple quasi-particle scheme. The calculated equilibrium lattice constants, bulk moduli, the pressure derivatives of the bulk moduli, and the A1 TO(GAMMA) phonon frequency are in good agreement with available experimental and other recent ab initio theoretical results. The self-energy band gap corrections are found to be highly kappa-dependent. The calculated fundamental band gap is direct in both cases and for the experimental lattice constant is calculated to be 3.36 eV in beta-GaN and 3.48 eV in alpha-GaN, in excellent agreement with experiment.